How to make Repeating Pattern Tiles and Molds: Page Two
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Sift plaster (I use Densite for molds-the expense easily offset by the life of the mold) over a screen to break up any lumps. Note: hard lumps in bagged plaster means the plaster has begun to hydrate and is no longer usable.

You can measure one part water to one and a half parts plaster (by weight) or you can use the "island" method, shown here. I recommend weighing, but I use this method a lot too.

When you have sifted as much plaster as the water will easily absorb islands will show, and stay, on the surface. Allow the plaster to "slake" for a minute or two. This allows air to escape from the plaster, and air bubbles are extremely undesirable.

You need to mix the plaster until all the lumps are gone. Using your hand will allow you to feel any lumps, but I recommend latex gloves as plaster will dry out skin. You can use a whisk but you must be very careful to avoid entraining air into the wet plaster.

The longer you mix, the faster the plaster will set. Using warm water will also speed up the reaction.

Pour the mixed, lump-free plaster gently through a screen to catch any impurities. Again, strive to avoid entraining air into the mold.

Any minor leaks can usually be plugged with a small wad of wet waste clay.

You may need to use bricks to weigh down large molds where the wooded flask tends to want to float on the plaster.

When the plaster has fully set you must remove the flask boards. This image shows the bottom of the mold with the boards removed.

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